Many kinds of silver halide color photographic materials and methods of forming color images are commercially available at the present time. Various improvements and inventions thereon have been made depending on the end use. It is generally required that silver halide emulsions employed in these photographic light-sensitive materials have high sensitivity. Therefore, silver iodobromide, silver chloroiodobromide and silver chlorobromide, etc., each being mainly composed of silver bromide, are used as the silver halide in the emulsions at present. Further, various kinds of development accelerators have been investigated in order to increase the color forming property and to shorten the processing time in color development during processing of color photographic light-sensitive materials. Particularly, benzyl alcohol is widely employed at present.
Recently, however, reduction of development processing time, simplification of the processing system and operation, and achievement of low environmental pollution have been under great demand, in addition to high sensitivity.
This demand for reduction of the period of time required to develop film, simplification of laboratory work, improvement in productivity, miniaturization, and simple operation of the processing system is mostly due to the advent of small scale laboratories, designated mini-labs, etc. With respect to meeting these requirements for rapid processing, simplification of the processing system, and achievement of low environmental pollution, benzyl alcohol, which is generally used in the color developing solution, causes severe problems.
Since benzyl alcohol has low water-solubility, it is necessary to use a solvent, such as diethylene glycol, etc., in order to assist dissolution of the benzyl alcohol. These solvents containing benzyl alcohol exhibit large values of BOD (biochemical oxygen demand) and COD (chemical oxygen demand) which indicate a heavy environmental pollution load. Therefore, it is desirable to eliminate these compounds in view of the need to preserve the environment. Also, it takes a long time to dissolve benzyl alcohol in a developing solution, even when the above described solvent is employed. Thus, elimination of benzyl alcohol is desired to simplify preparation of the developing solution.
However, to simply eliminate benzyl alcohol results in a severe lag in color development, which is contrary to the commercial need for rapid processing. Thus, a substitute for the use of benzyl alcohol has been desired.
Silver halides mainly composed of silver bromide, which have been employed the most until now, are disadvantageuous for rapid processing from a theoretical point of view, since bromine ions, which are released from the silver halides when they are developed, have a development inhibiting effect. For rapid processing, silver halides mainly composed of silver chloride are preferred. However, silver halide emulsions mainly composed of silver chloride have a disadvantage in that, while they have a high development speed, they are apt to fog. This causes a severe problem in the practical use, particularly in a green-sensitive silver halide emulsion layer containing a magenta dye forming coupler, silver visual sensitivity to magenta dyes is high.
Because of the disadvantages described above, it is difficult to obtain excellent developability with silver halides mainly composed of silver chloride when using methods of forming images having relatively high sensitivity.
Accordingly, many attempts have been made to overcome these disadvantages. For instance, in order to increase sensitivity, silver chlorobromide emulsions having a high silver chloride content which contain silver chlorobromide grains having a stratiform structure are known. These silver chlorobromide emulsions are described in detail, for example, in Japanese Patent Application (OPI) Nos. 95736/83, 108533/83, 222844/85 and 222845/85, etc. (the term "OPI" as used herein means an "unexamined published application"). Further, a method for increasing sensitivity by doping the inner portions of silver halide grains with metal ions is described in Japanese Patent Application (OPI) No. 135832/80. Fog also occurs during sensitization of the grains formed. Methods for restraining such a fog are described in Japanese Patent Application (OPI) Nos. 125612/83 and 47940/86.
Although various attempts for increasing sensitivity and restraining the formation of fog with respect to silver halides mainly composed of silver chloride have been made while maintaining their excellent developability, they are still insufficient and, thus, further improvement has been desired.